(1) Field of the Invention
The invention relates to a semiconductor device for cutting off high voltage that can protect internal components of the semiconductor device from the shock generated by the high supply power Vcc.
(2) Description of the Prior Art
Generally, an electrostatic discharge protection circuit is employed between supply power terminal and internal circuit to protect the internal components of a semiconductor chip from unstable high voltage applied from the supply power terminal.
FIG. 1 is a block diagram of a conventional semiconductor chip, showing an electrostatic discharge protection circuit that each channel of thick film transistor T1 and thin film transistor T2 is formed between a current path and ground Vss on both sides of resistance R1 on the current path connecting a supply power Vcc 11 with an internal circuit 13.
The transistor T1 of the supply power terminal 11 which is a thick film transistor, can protect the internal circuit from external shock of more than tens volts but cannot do it from external shock of 7 to 10 V. In case that the stable supply voltage is 5 V in a conventional semiconductor chip, the chip is designed to protect its internal circuit against about the supply voltage of 8 V higher than 5 V, which leads to high threshold voltage of the semiconductor device to drop the performance speed of the device, and since it is not possible to shorten the channel length of this conventional device, high integration of the semiconductor device cannot be obtained according to this technique.